Marios280Z

Captain Obvious, wow, that's impressive. Not sure where you got all the info about wire color coding, but I'm assuming it was somewhere in FSM or you actually had the relays appart once before. In either case, big thanks for the analysis.I'm very much visual guy when it comes to things like this so Iwould ahve to see it myslef to fully understand and folow your line of thoughts, but your theory seems to make sense. As I mentioned above, my oil sender unit connectors are oily, so perhaps that is part of it. I will be doing ground connections clena up this weekend and I will make sure to clean the oil sender as well (will have to probalb yreplace it soon). Thantks again for putting that much thouhg into this analysis.

sieunseen, I will try clamping the return line as well as tapping on the injectors. It actually takes just few (3) hours for the pressure to go to 0.

I do read FSM, I just have not gotten to all section of it . I have hard time following that fuel pump control system diagram... Not sure what to tell you about this pump and it being energized when ignition key goes to ON. I even spoke with the PO today and he said he never touched any wiring on the car. I have performed the Functional Test for fuel pump. Back then I did not have fuel pressure gauge to perform the discharge pressure test, but now since I do have the gauge I can do that test. But I want to challenge you guys on the fuel pressure thing. Wouldn't I have driveability problems as well if my fuel pressure wasn't high enough? Fixed. Yes, I do have the two prong oil pressure sender. I will look in the FSM for the section where it talks about the fuel pump relay and as Zed Head mentioned I will follow their test procedures. So here is what I have to do as my next steps as I gathered from you guys in the last couple of days: 1) Clean and verify all the ground wires in the engine bay are good 2) Perform fuel pressure discharge test per FSM 3) Perform fuel pump relay test per FSM I will also have my wife crank the car for me as I film the pressure gauge during priming and during cranking so you can have a look at it. Do we still look a the oil pressure sender as a potential offender?

My oil sender looks like the one for 3/77-84 280Z. I do have that two prong connector, unlike the earlier Zs that have that single nipple. I have read somewhere (it might have been the EFI bible or some other forum post) that I could trigger the fuel pump by setting ignition key to ON and moving the AFM flap passed the resting point. Is that not the case for my car because I have the trigger inside the oil pressure sender? I have noticed in the past that the connector on my oil sender unit is oily, as if the sender itself was slightly leaking the oil through the connector portion of the sender (white plastic and the prongs).

Are you thinking that the the fuel pressure drop may be caused by that possibly faulty connection in AFM? Or you're thinking that it may be causing hard start issue? Answering your question, yes, the AFM has been opened few years back by the previous owner and adjusted according to some procedure. I can find the paper work he gave me for it and let you know what the source of the procedure was. Keep in mind that he has never had this starting issue. From what he told me he was trying to adjust rich/lean fuel mixture. I have not had a chance to do any more testing and or ground connection cleaning last night so nothing to report.

Here is an exampe of how she starts up when she plays nice. This was caround 3 hours after I came back from wark. Engine wasn't hot, but it wasn't cold eithere, around 110 degrees according to the engine temp gage in tha car. I did prime the pump as before since the pressure was showing 0psi.

Yes, I did prime the fuel pump like I described above. I have though about TPS, but have not look into it.I was a bit "scared" to remove it since EFI bible talks about some very specific way of reconnecting the switch, and I did not want to mess it up. I leave my foot off the until (only sometimes) the very end when I see that engine is sputtering and is almost there to catch it, then I give it gentle tap.Sometimes it works, others it doesn't. Not sure what kind of explanation you are looking for. As i stated above: "Every time I turn key to ON, the fuel pressure increased by around 8-10psi, that's why I do it few times to get up to around 32. I have unplugged the starter and turn the ignition key to start, at which point I could actually hear the pump running." the fuel pump does not really run "run" with the ignition key in ON position. It looks more like it's getting energized just for a split of a second. I can definitely tell when pump is running when I disconnect the positive terminal from the starter and turn ignition key to start. As soon as I let go of the key I no longer hear the pump. As far as I know, and I can confirm with previous owner who never had this starting problem, the wiring on this car is all original and was not messed with, so I have hard time believing the ballast resistor is wired wrong. Dirty?-maybe. However, if the spark was week due to corroded/dirty wiring, I would most likely notice driveability issues other than just starting. I've performed several tests form FSM in the cold start department and have not found anything incorrect. There is definitely more tests to run, like the TPS. I've looked at that graph form FMS to try and get some clues on what may be causing the issue. When I pulled out the AFM the other day I got access to throttle plate. I used electrical connector cleaner and sprayed and wiped it inside. Got a lot of black grime out of there. I did that one evening and interestingly enough next morning the car started with a touch of a key! I was excited like a 5 year old in a candy store. later that afternoon when I was leaving work that car started nicely again- that was like Christmas in August. Unfortunately the next morning the problem came back as well as the following afternoon. In all the cases I primed the fuel pump as described above (I do try to stay consistent with the way I do/test things and try to varied only one variable at a time). I also did NOT change/adjust anything between the day the car started and the next day when it did not. Later today when I come back from work I will post a video of the car starting correctly, just as a reference to what it is capable of. I will perform all electrical connections/grounds clean up as described in the atlanticzcar post. I have done some of it (battery positive cable terminal replacement, thermotime switch and water temp sensor connector replacement, as well as AAR and CSV connector clean up.) Thanks for your help guys, and please keep throwing ideas at me.

No offense taken at all. I have thought about switching the thermotime switch and water temp sensor connectors. I believe they are OK a the bullet connector. They are color coded at that point, but I will double check that with continuity check. The starting issue began before I did almost any work under the hood, however I cannot recall is it started before or after install of new fuel filter. When I installed it I paid attention to the IN/OUT marking on it, but I will go back and double check my work. This morning (car sitting outside over night, the temps were around 60 degrees this AM) I recorded a video of a start up with the AAR bypass, as I mentioned in the previous post. As expected with the extra injection of air the RPMs went up almost to 2000rpm. I then immediately turn the engine off and attempted to start it again (in the past when I did that once the car fired right up). Unfortunately this time the trouble was still there. This test proved that the AAR is NOT the root cause of the issue, however it also proved that my AAR may not be operating 100% correctly since I get low idle RPM when engine is not warm - I'm guessing that AAR is not opening all the way.BTW, I have removed the AAR bypass before I drove to work. Here is the video: Let's get to the bottom of this guys...

Yes, the fact that I have to try 2,3, sometimes 4 times before the engine catches, the fact that it sputters before it dies, and the low idle on start up. I will take a video of how it starts when it is warm (with a touch of a key). I'm also concerned that if I don't get to the bottom of this I will have a heck of a time starting it when the temps start dropping to 40s and 30s (note, I will not be driving it in the winter). Also, one time I have started it cold (with the typical trouble, so it took me couple of tries), and about 2-3 seconds after it finly started I turned it off. Then attempted to start it again and the enging started right up...Not sure if it was just a fluke or what. Next time I encounter the difficulty I will repeat this test to see if it will start right up or not. Another point I should mentioneis the CSV test I performed. I pulled the CSV out of the intake manifold and put it in the jar. I had my wife crank the engine (when cold). There was no drop of fuel coming out of the CSV. Granted, it was about 85 degrees outside, so I don't know how valid the test was. I think the FSM talks about the upper temp limit for the thermotime switch being 70 degrees. At that point I also checked the wire continuity between the CSV connector and the thermotime switch and it was OK. On the other hand I had peopl tell me that they have entirly removed the CSV from their Z cars and never had problems starting even in cooler temps. You have a good point with that idle screw. But for tomorrow morning I will try with the AAR bypass.

Ha, you must have posted your last message as I was writing my response No biggy. I will let you know tomorrow if bypassing AAR helped to start the engine right up. Does anybody have any other idea what may be happening here? looks like we have a lot of audience Zed Hed,but nobody is pitching in

I'm not sure where your concern is coming from Zed Head. Right now it is isolated (air wise) from the engine. When the AAR is operating correctly during inital start up and is wide open, than it acts exactly like the hose I connected. The one end of the hose is connected before the throttle body to pick up the air, just like the AAR assembly does. Then istead of flowing through the assembly: the rubber hose--->metal pipe--->again to a short rubber hose---> to AAR valve---> to another short rubber hose--->to the emettal niple---> into the intake manifold PASSED the throttle body, I simply connected the two points prior to throttle body and passed the throttle body with just a continues hose. I was NOT going to drive it this way. I was going to ONLY start in the mornig to see how it would go. There is no signal to the ECU from the AAR at all, as you know.It's a dumb air passage with heating element to close it when things get warm. "2. Moved to front!~ - BUT. Your picture shows that you completely bypassed the throttle blade. The engine might go to sky-high RPM right away. Don't start it like that." That's exactly what the AAR does, it bypasses the throttle blade. From the EFI Bible: "You know that idle speed can be raised by simply bypassing throttle plate. During warm up, we do exactly that by using an air valve, called an Auxillary Air Regulator.(...)When the engine is cold the valve is open;so when the engine starts, ari can bypass the throttle plate and go through the valve." I'm not sure what you mean by: "Did that hose nipple on the big hose have a plug on it or was it open to air? It should be plugged, I believe."

Well,let's revisit the AAR. I installed bypass to AAR.See picture.will report tomorrow if it works.

ZedHed, you are right, in that video the RPM went to 1000. That's becuase I had my idle screw artificaly set to high so thtat during the start engin would run at higher RPM. That in turn casued increased RPM during idle once the engine warmed up. I have another vidoe over here that shows lower RPM: That's interesting theory about the starter. I don't have a problem starting it at any other times. Perhaps I just let go before the engine catches because I feel like I'm dragging the starter. Regarding fuel pressure. When I unplug the vacume hose, the pressure goes up to around 38-39 psi. I have found on one of the forums few people saying that 31/32 with the vac hose ON and 38-39 without the vac hose at idle is normal. Service manula talks about 36psi... Every time I turn key to ON, the fuel pressure increased by around 8-10psi, that's why I do it few times to get up to around 32. I have unplugged the starter and turn the ignition key to start, at which point I could actually hear the pump running. What I did with AAR is I removed it and put in in the fridge for few minutes. When I pulled it out the flap was 3/4 way open. Not sure if it will ever fully open from what I saw in a AAR fix DIY found on atlanticzcar website. I have not warmed it up to see if it would actually close the flap. I can try and do that. Any other suggestions?

Hi all, new guy here. I will take this opportunity to introduce myself and my car. About me My name is Mario, I live in Cedar Rapids, IA. I'm in my low 30s (for those who care), I like to work on cars, but I don't have a whole lot of detailed experience, however I'm very willing to learn. In early April igot the car (I wasn't necessarily looking for one, it found me). I've knew about 2X0Z for a while (my father in-law has two of 240Z sitting in his backyard rusting away ) but when this deal came I could not refuse. About the car 1978 280Z, 59,XXX miles when I got it. Original, survival (I have all the original paper work including signed contract from the dealer and window sticker). Never saw snow, rarely any rain. Previous owner had it for over 25 years and drove it maybe a 1000 miles a year. Always garaged. Few things he did to car: lower suspension with Tokico springs and adjustable shocks, big brake kit upfront, SS brake lines,cold air intake, newer spark plug wires, 2.5" exhaust form MSA, including down pipe and all the way to turbo muffler. Other than that all was stock, including all the engine gaskets! What I did when I got the car Replaced the fluids: engine oil and filter, rear diff, MT oil, coolant. replaced the spark plugs with with the stock NGK ones, replaced fuel filter, distributor cap and the rotor, replaced battery cables, installed new 16x8, 0 ofset XXR513 black/silver wheels that came with the purchase. The issue I have hard time starting the car after it sits for a while (for example a day at work). The car did not have this issue when I first got it, but slowly it developed it. One point to mention is that it started BEFORE I did any part replacement under the hood. Here is the link to a youtube video of wha the car does. Sometimes it is more sever, sometimes it is less sever: One additional point to mention is that the RPMs are typically low for "cool start". I would expect the RPMs to sit around 900-1000 when the engine is warming up and slowly come down to 700-800 rpms. It's as if the engine does not recognize the "cool start" and perhaps does not go into fuel enrichment period.The starting issue is there regardless of the outside temperature. It could be 85 or 60 degrees, still acts the same. Based on what I noticed this morning when I sarted the engine I'm thinking it has something to do with the air delivery. Right after I started the car (RPMs were hovering around 700) I went in and unplugged the vac hose between intake manifold and fuel pressure regulator. As soon as I unplugged it at the FPR and left it opened (therefore providing more air to the system), the engine reved up to around 800-900rpm. When I plugged the vac hose with my finger engine would drop rpms. After few minutes of running, this drop and rise of rpms was much lesser, if any at all. Here is what I did for troubleshooting so far I do have EFI bible and the Service Manual and I actually have performed quite a bit troubleshooting in the cold start department: replaced water temp sensor as well as water temp sensor connector, cleaned thermotime switch and replaced its electrical connector. I performed continuity/resistance/voltage tests as described in Service Manual at the ECU for water temp sensor, themotime switch, Cold Start Valve, and Auxiliary Air Recirculating valve. All checked out OK, unless I misinterpreted the results. I pulled out CSV, cleaned it externally and cleaned its electrical connector. I pulled the AAR valve and made sure that the internal flap was moving freely. I took out Air Flow Meter and made sure the flap was moving freely. I wiped it inside. Having AFM out gave me inside look at the throttle body, so I sprayed some electrical connector cleaner and wiped it clean (there was actually quite a bit black gunk that came out)...the starting problem persists.The fuel pressure is not maintained in my system. I installed inline fuel pressure gauge right after the fuel filter. The pressure drops to 0 after few hours of car being off. However, before I crank the car I prime the fuel pump by turning ignition to ON/OFF position 4-5 times, until I see that pressure gauge reads around 31 psi. Even then I still get the problem. ...I started to run out of ideas. ​What else can it be? One of the comments in my youtube video says it could be a vapor lock. If so, what could cause this vapor lock? Beside this starting issue I believe car drives well (I say believe, because I have never driven a Z so I don't have a benchmark to compare to). It feels like it pulls all the way through the RPM range. The only other thing I have noticed is that when I drive it harder I get slight afterfire when up shifting 1-->2 and 2-->3 gear. Help...